As shown in FIGS. 11 and 12, a prior-art door lock for an automotive vehicle includes a latch 1 operatively associated with a ball, not shown, and a base 3 on which the latch 1 is freely rotatably supported by a pin 2 fixedly secured to the base 3. The pin 2 has a flange 4 for retaining the latch 1 between itself and the base 3. A gap between the pin 2 and the wall of a pin insertion hole in the latch 1, and a gap between latch 1 and base 3 enable the latch 1 to move freely with respect to the base 3 and pin 2 but allow an abnormal noise to be produced due to impact between these metal components when the door is opened and closed. For this reason the latch 1 is equipped with a silencer 5. The latter includes a spacer portion 6 and a leaf spring portion 7. The spacer portion 6 is inserted into the pin insertion hole of latch 1, and the leaf spring portion 7 is interposed between the base 3 and latch 1 to urge the latch 1 into resilient contact with the flange 4 of pin 2. The spacer portion 6 suppresses movement of the latch 1 radially of the pin 2, and the leaf spring portion 7 prevents the latch 1 from striking the base 3, thereby minimizing the generation of abnormal noises when the door is opened and closed.
A problem encountered in this prior-art arrangement is that as the spring force of the leaf spring portion 7 is weakened its ability to limit backlash is impaired. Though this reduces the frictional resistance of the rotating surface of the latch, the silencing effect is adversely affected.
Accordingly, the prior-art approach inevitably is to provide the leaf spring portion 7 with a large spring force in order to minimize the generation of abnormal sounds produced by the striking contact between the latch 1 and base 3. However, when a large spring force acts upon the latch 1 at all times, the rotation of the latch 1 meets resistance over the entire region thereof, though the generation of abnormal sounds is indeed greatly reduced. When the door is opened from the completely closed state by pulling on the door opening handle, the latch cannot return to its original position merely under the force of a return spring because of the increased resistance memtioned above. Instead, the latch comes to reside at an intermediate position. This can impede the locking of the door.